An electrophysiologic diagnosis of mild carpal tunnel syndrome(CTS) is affected by laboratory error, diagnostic method, hand temperature and age of subject. To control for these variables and improve for detection of mild CTS, we have introduced comparative testing of other nerves in the same hand; median to radial sensory latency difference(MRLD, <0.5 msec in normals), median to ulnar sensory latency difference(MULD, ≤0.4 msec in normals), ratio of median palm latency(MPL/MSL, >0.44 in normals). One hundred and twenty-eight patients with the clinical symptoms consistent with CTS and 53 persons as control, invited Kyung Hee medical center from 1992 to 1993 year were studied. Among 45 patients diagnosed to mild CTS, there were thirty-two females(73.3%), 29(65.9%) aged 40 to 59 years and 9(17.8%) affected bilaterally. The MRLD, MULD, MPL/MSL, MSL and MML had sensitivity of 86.8%, 62.3%, 7.5%, 58.5% and 54.7% in turn. Therefore, MRLD may be a sensitive indicator of mild CTS that can be measured quickly with a minimum of discomfort. We recommend our method for screening of mild CTS before other specific study.